Custom functions in Processing Language

Also your function is not returning a value, which will give you an error. It looks like you are confusing things. Either declare it a void or return a value of declared type (that last is what your assignment calls for). Either way a function, or a method, needs to be called to execute, and you are not calling it! So the code inside your the function is not being run!! The following:

void imAMethod()
{
  println("hello");
}

It is a valid method, but will do nothing, you need to call it, like:

imAMethod();// calling your method

void imAMethod()
{
  println("hello");
}

But this won't work also, will give you the error "It looks like you're mixing "active" and "static" modes". Thats because to use a function in Processing you need to have at least a setup() method in the sketch, so:

 void setup()
{
  imAMethod();
}//end of setup

void imAMethod()
{
println("hello");
}

will work as expected.

But you need a function, so as Jesper pointed you will have to do something like:

int a = 30; // those are global variables to pass to your function
int b = 20;
void setup()// this is a builtin basic Processing method
 {
   //call your function 
   println("The sum of " + a + " and " + b + " is "+ twoNumbers(a, b));
 }

int twoNumbers(int a, int b)
{ 
//do your math and tests here
return result;
}

There is another thing not clear in the assignment. A function must return something, so it is not clear what the function should return if a is not greater than b. You will have to handle this case, or compiler will complain. You may want to move this test out of the function to make things easier, like:

if (a < b)
println("The sum of " + a + " and " + b + " is "+ twoNumbers(a, b));//call your function
else
println(a + " is smaller than " + b);

and in the function just do the sum. But this may be not what the assignment requires... Anyway you will need to return something even if a is not greater than b. Note that the printing to console can be done inside the function also.

Hummm, re reading the assignment a think what is expected is: Aways return the sum, and just print if a is greater than b, which makes more sense and is easier, something like:

int twoNUmbers(int a, int b)
{
 if (a < b){/*print the string*/}
 return a + b;
}

Just a note for jlordo. In Processing.org you don't have a main, or better, it is transparent/hidden from user. Processing is like a "dialect" of java. So the code above would run as it is. There are two basic builtin functions: setup() and draw(). If the user do not use none of them the IDE will warps it in a setup() function, that will call the main() somewhere else. It will run once. Draw() instead loops forever.